Actuators adapted for the sliding means to move and guide linearly any object are recently availed in extensively increased fields. Modern actuators are needed to be less in weight as well as in height in transverse section, and more compact in construction. The actuators of the sorts as stated earlier have been used in means to do reciprocating motion, for example, in assembling machines, measurement instruments, various machines, industrial robots, semiconductor manufacturing equipments, and so on.
Disclosed in the commonly assigned Japanese Laid-Open Patent Application No. 2002-147 561 a ball screw device in which the lubricating means is attached to one end of the ball screw nut. The lubricating means is composed of which is composed of holder to fit detachably over a wiper seal and more than one lubricating plates stowed in the holder. The lubricating plate has a C-shaped contour in front view and a tongue coming into sliding engagement with a helical groove around the ball screw to apply lubricant to the helical groove. The lubricating plate is made of porous compact of sintered resinous material, which has a polarity of open-pores or open-cells impregnated with a plenty of lubricant.
The commonly-assigned Japanese Laid-Open Patent Application No. 2010-138 981 discloses an actuator composed of an elongated frame and a slider both of which are made of light alloy and made with dovetail grooves into which guide rail members of stainless steel fit to provide load-carrying races. Thus, the actuator is made light weight and compact in construction. With the actuator constructed as stated earlier, both the frame and the slider are made of extruded shapes of light-metal alloy and the first guide rail members may be attached to the frame with simple structure. Upper sealing members are placed between the frame and the slider. The frame is made an elongated extrusion of U-shape in transverse section whose side walls have first recesses of dovetail configuration to fit over first rail members and flanges. A slider has therein the slider body having second recesses of rectangular shape to fit over second rail members. There is further provided a driving unit to force the slider with respect to the frame. The first rail members each have the wedged configuration including tapered contours and dents, while the second rail members each have the rectangular shape.
With the prior ball screw device with lubricating means recited earlier, as nut is combined with the holder which contained therein the lubricating plates, the nut is inevitably made longer by the lubricating plates in the overall length and correspondingly the stroke length of the slider is restricted. With the prior actuator recited later, the actuator composed of an elongated frame and a slider, though weighing less, is made larger or bulky in construction. Advanced actuator designed to move unidirectionally is increasingly made lighter in weight as well as more compact in construction and more inexpensive than ever. Moreover, the advanced actuator in addition to compact in construction is needed to accomplish maintenance-free lubrication, less height in transverse section, and simple and inexpensive in construction.